Science academies: ocean acidification must be on CO2 agenda

The United Nations Framework Convention on Climate Change (UNFCCC), which helped usher in the Kyoto Agreement that was intended to limit emissions of greenhouse gasses, is now gearing up for the next major round of climate talks, which will take place in December, hosted by Copenhagen, Denmark. Many are hoping that the successor to Kyoto will provide comprehensive targets for emissions, and involve many more nations in the framework. But the national scientific academies of 70 nations have issued a statement warning that the exclusive focus on climate change may result in plans that ignore an equally significant risk: ocean acidification.

The statement was organized by the Interacademy Panel, which is an international umbrella group that coordinates the activities of national and regional science organizations. In this case, the IAP has gotten 70 academies to sign on, including some from nations that will be pivotal in the Copenhagen negotiations, such as the US, China, India, and Japan, although Russia appears to be absent. The sense that scientific issues transcend political disputes is reinforced by some of the strange bedfellows among the signatories. It's not often you see national organizations from the US, Cuba, and Venezuela signing on to the same document, or Iran, Israel, and the Palestinians endorsing a single position.

To avoid the worst of the consequences, the statement argues that we need to cut global CO2 emissions in half by the century's midpoint; that's significantly more aggressive than many of the plans that have been proposed to address climate change, which focus on goals for the century's end.

The document emphasizes that the oceans, by acting as a sink for carbon dioxide emissions, are both an inseparable part of the climate change equation, and pose some distinct risks that should not be ignored. The scale of the oceans and their ability to absorb carbon dioxide in the atmosphere, both by dissolving it and by hosting organisms that metabolize it, make them a key part of the atmospheric carbon cycle. The statement cites estimates that about a quarter of humanity's CO2 emissions over the past 200 years have wound up in the oceans; without that, climate change would have been more dramatic.

But, when dissolving in water, CO2 forms a weak acid and, in the process, changes the chemistry of the oceans. Just as the current atmospheric levels of CO2 haven't been seen in over 800,000 years, there are changes in the ocean chemistry that haven't been seen for a similar length of time. Since preindustrial times, the statement notes, pH levels have dropped by 0.1 unit, which may not sound like much until you consider that pH is measured on a logarithmic scale (the authors conveniently rephrase this as "a 30 percent increase in hydrogen ion activity").

The excess dissolved CO2 is likely to affect the oxygen/CO2 exchange of metabolically active species—the statement cites squid as being especially vulnerable. But the key impact is on carbonate ions, as many organisms use carbonate compounds to build structures that range from the microscopic, though the shells of mollusks, and up to geographic features like coral reefs. "Carbonate ion concentrations are now lower than at any other time during the last 800,000 years," the authors note, and we're on track for even bigger changes: "projections suggest that by mid-century CO2 concentrations will be more than double preindustrial levels and the oceans will be more acidic than they have been for tens of millions of years. The current rate of change is much more rapid than during any event over the last 65 million years. These changes in ocean chemistry are irreversible for many thousands of years, and the biological consequences could last much longer."

The authors state that, at current rates of CO2 emissions, ecosystems in polar waters will be under severe stress within the next 50 years. They recognize that some species will do well in the changed conditions; for example, a recent study shows that a species of sea star likes warm, acidic water, even though it results in a reduction of the organism's calcified structures. Still, it will be difficult to avoid a generalized disruption of oceanic ecosystems, with obvious consequences for cultures that rely on the sea as a food source.

To avoid the worst of the consequences, the statement argues that we need to cut global CO2 emissions in half by the century's midpoint; that's significantly more aggressive than many of the plans that have been proposed to address climate change, which focus on goals for the century's end. It calls on the Copenhagen negotiators to set this as a goal. The authors also highlight the fact that reducing carbon dioxide emissions is the only way to tackle the problem; various geoengineering proposals would avert rising temperatures by limiting incident sunlight, but those won't slow the drop in oceanic pH. And, finally, the statement calls upon other measures to reduce the stress on oceanic ecosystems, such as further efforts to limit overfishing.

The release of the statement was announced by the Chinese Minister of Health, Chen Zu, and Howard Alper, the president of Canada's Science, Technology and Innovation Council. "The implications of ocean acidification cannot be overstated," the duo said. "There has been much talk among the science community over the past few years about ocean acidification and its potentially catastrophic consequences, but it has failed to receive the political attention it demands. Its absence from discussions to-date is of immense concern, and we call for its immediate inclusion as a vital part of the climate change agenda."

Although this statement is addressed towards policy makers, realistically, it seems that many of them are already convinced action is necessary, but are constrained by economic and political concerns. The key factor may be whether the process of ocean acidification and its consequences are accessible enough to register with the public that establishes these constraints.